<template>
  <div class="spec-preview">
    <img :src="imgObj.imgUrl" />
    <div class="event" @mousemove="handler"></div>
    <div class="big">
      <img :src="imgObj.imgUrl" ref="big"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    data() {
      return {
        currentIndex:0
      }
    },
    props:["skuImageList"],
    computed:{
      imgObj(){
        return this.skuImageList[this.currentIndex]||{}
      }
    },
    mounted(){
      //联系全局事件总线
      this.$bus.$on('getIndex',(index)=>{
        this.currentIndex = index
      })
    },
    methods: {
      handler(event){
        //遮罩元素
        let mask = this.$refs.mask
        let big = this.$refs.big
        //遮罩 距离父盒子的左值 event.offsetY垂直值 
        //offsetWidth 获取元素宽度  mask.offsetWidth/2 遮罩元素的宽的2分之一
        //offsetX 获取x轴坐标
        //算出来的是遮罩元素和父元素的距离
        let left = event.offsetX - mask.offsetWidth/2
        let top = event.offsetY - mask.offsetHeight/2
        //修改遮罩元素的左右属性值，让他等于鼠标的属性值，就实现了移动
        if(left<=0)left=0
        if(left>=mask.offsetWidth)left=mask.offsetWidth
        if(top<=0)top=0
        if(top>=mask.offsetHeight)top=mask.offsetHeight
        //遮罩左右属性
        mask.style.left = left+"px"
        mask.style.top = top+"px"
        //放大图
        //放大图是原图两倍所以要*2，然后放大图和原图移动方向相反所以是 -（负数）
        big.style.left = - 2 * left+"px"
        big.style.top =  - 2 * top+"px"
      }
    },
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>